Apparatus and method for generating and transmitting reference signal in radio communication

ABSTRACT

It is possible to provide a radio communication terminal device and a radio transmission method which can improve reception performance of a CQI and a reference signal. A phase table storage unit stores a phase table which correlates the amount of cyclic shift to complex coefficients {w1, w2} to be multiplied on the reference signal. A complex coefficient multiplication unit reads out a complex coefficient corresponding to the amount of cyclic shift indicated by resource allocation information, from the phase table storage unit and multiplies the read-out complex coefficient on the reference signal so as to change the phase relationship between the reference signals in a slot.

BACKGROUND

Technical Field

The present invention relates to a radio communication terminalapparatus and a radio transmission method.

Description of the Related Art

3GPP-LTE (3rd Generation Partnership Project-Long Term Evolution) hasdiscussed a transmission method for uplink control channels in differenttwo ways: “in a case in which uplink control signals and uplink data aretransmitted simultaneously”; and “in a case in which uplink controlsignals and uplink data are not transmitted simultaneously.”

When uplink control signals and uplink data are transmittedsimultaneously, preferably, control signals are transmitted insynchronization with data using uplink resources designated by the basestation. Meanwhile, when uplink data signals are not permitted to betransmitted and therefore uplink control signals are not transmitted insynchronization with uplink data, terminals transmit uplink controlsignals using “a band for transmitting uplink control signals” reservedin advance.

A band (PUCCH: Physical Uplink Control Channel) that is reserved fortransmitting uplink control signals (e.g. ACK/NACKs and CQIs) by3GPP-LTE is shown in FIG. 1. In FIG. 1, the vertical axis represents thesystem bandwidth of which values unique to the base station, forexample, 5 MHz or 10 MHz are set, and the horizontal axis representstime. One subframe length is 1 ms, and PUCCH transmission is performedper subframe. In addition, one subframe is composed of two slots. Asshown in FIG. 1, frequency resources allocated to control signals arefrequency-hopped at the time slots are switched, so that it is possibleto obtain the frequency diversity effect.

Moreover, FIG. 2 is a drawing conceptually showing a state in whichterminals transmit CQIs using a band reserved by the system. Here, eachZAC sequence in the figure has a sequence length of twelve in the timedomain, and has a characteristic of constant Amplitude (CA) in thefrequency domain and the characteristic of zero auto correlation (ZAC)in the time domain.

Each slot of a subframe for transmitting CQIs is formed by seven SC-FDMA(Single Carrier-Frequency Division Multiple Access) symbols. HereinafterSC-FDMA symbols in a slot are referred to as the first, second, . . . ,seventh SC-FDMA symbols. CQI signals are placed in the first, third,fourth, fifth and seventh SC-FDMA symbols and reference signals (RSs)for demodulating CQIs are placed in the second and sixth SC-FDMAsymbols. As shown in FIG. 2, each of five CQI symbols is primarilyspread by a ZAC sequence in the frequency domain, and placed in aSC-FDMA symbol (or “LB”: Long Block). In addition, reference signalsobtained by performing the IFFT (Inverse Fast Fourier Transform) of ZACsequences represented in the frequency domain are placed in the secondand sixth SC-FDMA symbols.

ZAC sequences and amounts of cyclic shift used in each terminal aredetermined according to commands from the base station. Here, althoughcyclic shifting means transforming the waveform of ZAC sequencestransformed in the time domain using cyclic shifting, an equivalentprocessing is possible by phase rotation in the frequency domain, sothat a state in which cyclic shift processing is performed in thefrequency domain is shown here. In addition, it has been determined thatCQIs from different terminals are code-multiplexed (CDM). To be morespecific, CQI signals from different terminals are transmitted throughthe same ZAC sequences having different amounts of cyclic shift. On thebase station side, it is possible to separate CQI signals from terminalsby taking into account of the amount of cyclic shift per terminal aftercorrelation processing with ZAC sequences. That is, CQIs from differentterminals are code-multiplexed.

In addition, 3GPP-LTE has determined that, when one terminal transmitsCQIs and response signals (ACK/NACKs) simultaneously, response signalsmay be transmitted using reference signals for demodulating CQIs. Thedetails are described later.

FIG. 3 is a drawing showing the characteristic of ZAC sequences used toprimarily spread CQIs in the time domain. Each ZAC sequence has asequence length of twelve in the time domain, and therefore there aremaximum twelve patterns of cyclic shift. Since the cross-correlationbetween the same ZAC sequences having different amounts of cyclic shiftis approximately zero, it is possible to separate signals spread throughthe same ZAC sequences having different amounts of cyclic shift in thetime domain almost without interference.

However, although in an ideal environment as shown in FIG. 3, it ispossible to separate signals spread by means of ZAC sequences withdifferent amounts of cyclic shift without interference from each otherby correlation processing on the receiver side, those signals do notnecessarily reach the base station side simultaneously, due to theinfluence of channel delay, difference between timings terminalstransmit signals, frequency offset and so forth. By this influence oftiming difference, for example, as shown in FIG. 4, separationcharacteristics of signals spread by sequences corresponding to adjacentcyclic shifts are likely to deteriorate. In addition, the difference intransmission timings of terminals exerts a negative influence on theorthogonality between adjacent cyclic shifts of ZAC sequences. Forexample, in FIG. 3, assuming that amounts of cyclic shift obtained byshifting sequences one by one (twelve sequences of cyclic shift indexesi=0 to 12) is allocated to each terminal, it is possible to multiplexmaximum twelve terminals according to differences in the amount ofcyclic shift. That is, it is possible to code-multiplex twelve CQIsignals using one frequency resource.

Methods of transmitting CQIs in a PUCCH field reserved for transmittingcontrol information are described in non-patent documents 1 to 3. WithNon-Patent document 1, when only CQIs are transmitted, the phasedifference between two reference signals in a slot is fixed regardlessof the amount of cyclic shift as shown in FIG. 2.

In addition, with non-patent documents 2 and 3, when CQIs and responsesignals are transmitted simultaneously, response signals are representedby multiplying CQI demodulating reference signals by complexcoefficients {w1, w2} As shown in FIG. 5 That is, a case of {w1,w2}={+1, +1} represents ACK information and a case of {w1, w2}={+1, −1}represents NACK information. In addition, the relationship betweenACK/NACKs and {w1, w2} is not changed regardless of the amount of cyclicshift.

Non-Patent Document 1: R1-074010, Motorola, “Uplink Transmission of CQIand ACK/NAK”, 3GPP TSG RANI #50-bis, Shanghai, China, Oct. 8-12, 2007Non-Patent Document 2: R1-074097, Samsung, “Multiplexing CQI and ACK/NAKTransmission in E-UTRA UL”, 3GPP TSG RAN WG1 #50b is, Shanghai, China,Oct. 8-12, 2007

Non-Patent Document 3: R1-074141, Texas Instruments, “Simultaneous CQIand ACK/NACK Transmission in Uplink”, 3GPP TSG RAN WG1 #50b, Shanghai,China, Oct. 8-12, 2007

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

According to 3GPP-LTE, as described above, CQI signals from eachterminal are multiplexed in different amounts of cyclic shift as shownin FIG. 6. That is, CQI signals are identified based solely on thedifference in the amount of cyclic shift. In an ideal environment, sinceZAC sequences corresponding to different amounts of cyclic shift areallocated to CQI signals from each terminal, it is possible to separatesignals without interference.

However, the orthogonality of cyclic shift sequences is broken downdepending on channel delay conditions and so forth as described above.FIG. 7 shows a delay profile in the time domain after the base stationreceives CQI signals transmitted from plurality of terminals andperforms correlation processing. As shown in FIG. 7, if theorthogonality of cyclic shift sequences is broken down, interferenceoccurs between CQI signals allocated to adjacent cyclic shift sequences.This interference between cyclic shift sequences exerts a negativeinfluence on CQI signals and reference signals, and therefore, theaccuracy of channel estimation and the CQI demodulation performancedeteriorate.

It is therefore an object of the present invention to provide a radiocommunication terminal apparatus and a radio transmission method thatimprove the capability to receive CQIs and reference signals.

Means for Solving the Problem

The radio communication terminal apparatus according to the presentinvention adopts a configuration including: a reference signalgenerating section that generates a reference signal by controlling aphase difference between a plurality of reference signals included in aslot in accordance with a cyclic shift index allocated to the radiocommunication terminal apparatus; and a transmitting section thattransmits the generated reference signal.

The radio transmission method according to the present inventionincludes the steps of: generating a reference signal by controlling aphase difference between a plurality of reference signals included in aslot in accordance with a cyclic shift index allocated to a radiocommunication terminal apparatus; and transmitting the generatedreference signal.

Advantageous Effects of Invention

According to the present invention, it is possible to improve thecapability to receive CQIs and reference signals.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a drawing showing a band reserved for uplink control signaltransmission;

FIG. 2 is a drawing conceptually showing a state in which terminalstransmit CQIs using a band reserved by the system;

FIG. 3 is a drawing showing the characteristic of ZAC sequences used toCQI primary spread;

FIG. 4 is a drawing showing states in which separation characteristicsof signals spread by adjacent cyclic shift sequences deteriorate;

FIG. 5 is a drawing conceptually showing a state in which CQIs andreference signals are transmitted simultaneously;

FIG. 6 is a drawing showing a state in which CQI signals from eachterminal are multiplexed in different amounts of cyclic shift;

FIG. 7 is a drawing showing a state in which interference occurs betweenCQI signals allocated to adjacent cyclic shift sequences;

FIG. 8 is a block diagram showing a configuration of a terminalapparatus according to embodiment 1 of the present invention;

FIG. 9 is a block diagram showing a configuration of a base stationapparatus according to embodiment 1;

FIG. 10 is a block diagram showing another configuration of a terminalapparatus according to embodiment 1;

FIG. 11 is a block diagram showing another configuration of the basestation apparatus according to embodiment 1;

FIG. 12 is a block diagram showing a configuration of a terminalapparatus according to embodiment 2 of the present invention;

FIG. 13 is a drawing showing a state in which complex coefficients areswitched according to phase switching signals;

FIG. 14 is a block diagram showing a configuration of a base stationapparatus according to embodiment 2 of the present invention;

FIG. 15 is a block diagram showing a configuration of a terminalapparatus according to embodiment 3 of the present invention;

FIG. 16 is a drawing showing an example of allocation of complexcoefficient patterns when CQIs and ACK/NACKs are transmittedsimultaneously; and

FIG. 17 is a block diagram showing a configuration of a base stationapparatus according to embodiment 3 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, embodiments of the present invention will be described in detailwith reference to the accompanying drawings. Here, with embodiments,components with the same functions will be assigned the same referencenumerals and overlapping descriptions will be omitted.

Embodiment 1

The configuration of terminal apparatus 100 according to embodiment 1 ofthe present invention will be explained with reference to FIG. 8. InFIG. 8, control information generating section 101 generates CQI signalsbased on downlink SIR (Signal to Interference Ratio) and so forth andoutputs them to coding section 102. Coding section 102 encodes thecontrol information outputted from control information generatingsection 101 and outputs the encoded control information to modulatingsection 103. Modulating section 103 modulates the coded controlinformation outputted from coding section 102 and outputs the result tospreading section 105.

ZAC sequence generating section 104 generates ZAC sequences and outputsthem to spreading section 105. Spreading section 105 spreads the controlinformation outputted from modulating section 103 using ZAC sequencesoutputted from ZAC sequence generating section 104 and outputs theresults to mapping section 106.

Mapping section 106 maps the signals outputted from spreading section105, maps them to frequency resources designated by resource allocationinformation and outputs the mapped control signals to IFFT section 107.IFFT section 107 performs IFFT (Inverse Fast Fourier Transform)processing of the control information outputted from mapping section 106and outputs the control information to which IFFT processing has beenapplied, to cyclic shift section 108. Cyclic shift section 108 performscyclic shifting during a predetermined time length designated byresource allocation information and outputs the results to CP addingsection 109. CP adding section 109 adds CPs (Cyclic prefixes) to signalsoutputted from cyclic shift section 108 and outputs the results tomultiplexing section 118.

In reference signal generating section 110, ZAC sequence generatingsection 111 generates ZAC sequences and outputs them to complexcoefficient multiplying section 113. Phase table storing section 112stores a phase table associating complex coefficients by which referencesignals are multiplied, with amounts of cyclic shift. Complexcoefficient multiplying section 113 reads the stored complexcoefficients. Here, the phase table will be described in detail later.

Complex coefficient multiplying section 113 reads complex coefficientscorresponding to the amount of cyclic shifts (Cyclic shift indexes)designated by resource allocation information from phase table storingsection 112, multiplies ZAC sequences by the read complex coefficientsand outputs the results to mapping section 114.

Mapping section 114 maps ZAC sequences outputted from complexcoefficient multiplying section 113 to frequency resources designated byresource allocation information and outputs the mapped signals to IFFTsection 115. IFFT section 115 performs IFFT processing of ZAC sequencesoutputted from mapping section 114 and outputs the signals to which IFFTprocessing has been applied, to cyclic shift section 116.

Cyclic shift section 116 performs cyclic shifting for a predeterminedtime length designated by resource allocation information and outputsthe results to CP adding section 117. CP adding section 117 adds CPs tothe signals outputted from cyclic shift section 116 and outputs theresults to multiplexing section 118.

Multiplexing section 118 time-multiplexes control information outputtedfrom CP adding section 109 and reference signals outputted from CPadding section 117, and outputs the results to radio transmittingsection 119. Radio transmitting section 119 performs transmissionprocessing, including D/A conversion, up-conversion, amplification andso forth, of signals outputted from multiplexing section 118, andtransmits the signals to which transmission processing has been applied,from antenna 120 by radio.

Next, the above-described phase table storing section 112 will beexplained specifically. Phase table storing section 112 has a phasetable associating cyclic shift indexes and complex coefficients {w1, w2}in table 1.

TABLE 1 Cyclic shift index w1 w2 0 +1 +1 1 +1 −1 2 +1 +1 3 +1 −1 4 +1 +15 +1 −1 6 +1 +1 7 +1 −1 8 +1 +1 9 +1 −1 10 +1 +1 11 +1 −1

Complex coefficient multiplying section 113 determines, for the secondand sixth SC-FDMA symbols for transmitting reference signals, complexcoefficients {w1, w2} corresponding to cyclic shift indexes (i=0, 1, . .. , 11) reported from the base station, from the phase table, andmultiplies ZAC sequences outputted from ZAC sequence generating section111 by the complex coefficients.

Now, the configuration of base station apparatus 200 according toembodiment 1 of the present invention will be explained with referenceto FIG. 9. In FIG. 9, radio receiving section 202 performs receptionprocessing, including down-conversion, A/D conversion and so forth, ofsignals received via antenna 201 and outputs the results to CP removingsection 203. CP removing section 203 removes the CPs of signalsoutputted from radio receiving section 202 and outputs the results toseparating section 204. Separating section 204 separates signalsoutputted from CP removing section 203 into reference signals andcontrol signals, outputs the resulting reference signals to complexcoefficient multiplying section 206 and outputs the resulting controlsignals to FFT section 216.

In channel estimating section 205, complex coefficient multiplyingsection 206 reads complex coefficients corresponding to the amount ofcyclic shift designated by resource allocation information from phasetable storing section 207 and multiples reference signals outputted fromseparating section 204 using the read complex coefficients. To be morespecific, the reference signals placed in the second and sixth SC-FDMAsymbols are multiplied by the complex conjugates of the complexcoefficients {w1, w2} multiplied in complex coefficient multiplyingsection 113 on the transmitting side. The reference signals by which thecomplex coefficients are multiplied, are outputted to in-phase addingsection 208. Here, phase table storing section 207 has the same table asthe table provided in phase table storing section 112 in terminalapparatus 100.

In-phase adding section 208 averages a plurality of reference signals ineach slot outputted from complex coefficient multiplying section 206.That is, reference signals placed in the second and sixth SC-FDMAsymbols are averaged (in-phase addition). The averaged reference signalsare outputted to FFT section 209.

FFT section 209 performs FFT processing of reference signals outputtedfrom in-phase adding section 208, transforms the resulting signals fromtime domain signals to frequency domain signals, and outputs thetransformed frequency domain reference signals to demapping section 210.Demapping section 210 captures signals from frequency resourcesdesignated by resource allocation information and outputs the signals tocorrelation processing section 212.

ZAC sequence generating section 211 generates the same ZAC sequences asthe ZAC sequences generated from terminal apparatus 100 and outputs themto correlation processing section 212. Then, correlation processingsection 212 performs correlation computation using the ZAC sequencesoutputted from demapping section 210 and the ZAC sequences outputtedfrom ZAC sequence generating section 211 and outputs the computationresult to IDFT section 213. IDFT section 213 performs IDFT (InverseDiscrete Fourier Transform) processing of the signals outputted fromcorrelation processing section 212, transforms the resulting signalsfrom frequency domain signals to time domain signals and outputs theresults to mask processing section 214. Mask processing section 214extracts only the range in which there are signals of the desired wave,using the amount of cyclic shift allocated by terminal apparatus 100,and outputs the result to DFT section 215. DFT section 215 performs DFTprocessing of the correlation values outputted from mask processingsection 214 and outputs the correlation values to which DFT processinghas been applied, to frequency domain equalizing section 218. Here, thesignals outputted from DFT section 215 represent frequency variation ofchannels and have the same channel estimation value for each of CQIsymbols (the first, third, fourth, fifth and seventh SC-FDMA symbols)because channel estimation values are calculated by in-phase addition.

FFT section 216 performs FFT processing of control signals outputtedfrom separating section 204, transforms the resulting signals from timedomain signals to frequency domain signals and outputs the results todemapping section 217. Demapping section 217 captures signals fromfrequency resources designated by resource allocation information andoutputs the signals to frequency domain equalizing section 218.Frequency domain equalizing section 218 performs equalization processingof control information outputted from demapping section 217 using thechannel estimation values (estimation values of frequency variationcaused in channels) outputted from channel estimating section 205 andoutputs the signals to which equalization processing has been applied,to correlation processing section 220.

ZAC sequence generating section 219 generates the same sequences as theZAC sequences generated by terminal apparatus 100 and outputs them tocorrelation processing section 220. Correlation processing section 220performs correlation computation using control information outputtedfrom frequency domain equalizing section 218 and ZAC sequences outputtedfrom ZAC sequence generating section 219, and outputs the computationresult to IDFT section 221. IDFT section 221 performs IDFT processing ofsignals outputted from correlation processing section 220, transformsthe resulting signals from frequency domain signals to the time domainsignals, and outputs them to mask processing section 222. Maskprocessing section 222 extracts only the range in which there aresignals of the desired wave, using the amount of cyclic shift allocatedin terminal apparatus 100, and outputs the result to demodulatingsection 223. Demodulating section 223 performs demodulation processingof control signals outputted from mask processing section 222 andoutputs the signals to which demodulation processing has been applied,to decoding section 224. Decoding section 224 performs decodingprocessing of the signals to which demodulation processing has beenapplied, and extracts control signals.

As described above, it is possible to reduce interference from referencesignals placed in adjacent cyclic shifts and therefore it is possible toimprove the accuracy of channel estimation. Here, since the degree ofimprovement effect differs between in-phase addition and linearinterpolation processing, each effect will be described individually.

First, with in-phase addition, since the phase of reference signals ischanged in accordance with cyclic shift positions, it is possible toprevent in-phase interference between two reference signals, so that theSIR of reference signals is improved and therefore it is possible toimprove the accuracy of channel estimation for all CQI symbols (thefirst, third, fourth, fifth and seventh SC-FDMA symbols).

Next, with linear interpolation processing, since it is possible toprevent in-phase interference between two reference signals, it ispossible to reduce interference to CQI symbols (the third, fourth andfifth SC-FDMA symbols) sandwiched between reference signals byinterpolation processing, so that it is possible to improve the accuracyof channel estimation. Here, although the interference power outsidereference signals (the first and seventh SC-FDMA symbols) is increasedby linear interpolation, the effect of reducing interference increasesas the number of symbols (the third, fourth and fifth SC-FDMA symbols)inside reference signals increases. In addition, symbols outsidereference signals are not subjected to interpolation processing, so thatit is possible to prevent an increase in interference.

As described above, according to embodiment 1, the phase relationshipbetween reference signals in each slot is changed by associating amountsof cyclic shift with complex coefficients {w1, w2} and multiplyingreference signals by complex coefficients corresponding to amounts ofcyclic shift, so that it is possible to reduce interference fromreference signals placed in adjacent cyclic shifts, and therefore it ispossible to improve the capability to receive CQIs and referencesignals.

Here, with the present embodiment, although the phase table shown intable 1 is taken as an example, the relationship between even-numberedcomplex coefficients {w1, w2} and odd-numbered complex coefficients {w1,w2} may be switched as a phase table 2 shown in table. 2

TABLE 2 Cyclic shift index w1 w2 0 +1 −1 1 +1 +1 2 +1 −1 3 +1 +1 4 +1 −15 +1 +1 6 +1 −1 7 +1 +1 8 +1 −1 9 +1 +1 10 +1 −1 11 +1 +1

Here, with the present embodiment, although the phase table shown intable 1 is taken as an example, {w1, w2}={+1, −1} in the odd-numberedcyclic shift indexes may be {w1, w2}={−1, +1} as a phase table 3 shownin table 3.

TABLE 3 Cyclic shift index w1 w2 0 +1 +1 1 −1 +1 2 +1 +1 3 −1 +1 4 +1 +15 −1 +1 6 +1 +1 7 −1 +1 8 +1 +1 9 −1 +1 10 +1 +1 11 −1 +1

Here, with the present embodiment, although the phase table shown intable 1 is taken as an example, cyclic shifting may be used every N(here, N=1) sequences as a phase table 4 shown in table 4. In table 4,complex coefficients {w1, w2} are not associated with odd-numberedcyclic shifts.

TABLE 4 Cyclic shift index w1 w2 0 +1 +1 1 −(N/A) − 2 +1 −1 3 − − 4 +1+1 5 − − 6 +1 −1 7 − − 8 +1 +1 9 − − 10 +1 −1 11 − −

Here, with the present embodiment, processing performed in the timedomain in cyclic shift sections 108 and 116 in terminal section 100 asshown in FIG. 8 may be equally performed in the frequency domain inphase rotation processing sections 151 and 152 as phase rotationprocessing as shown in FIG. 10.

In addition, with the present embodiment, although a case has beenexplained where base station apparatus 200 calculates channel estimationvalues by in-phase addition processing as shown in FIG. 9, the presentinvention is not limited to this, and interpolation processing section251 may calculate channel estimation values by linear interpolationprocessing. In a case of linear interpolation processing, channelestimation values for CQI symbols (the first, third, fourth, fifth andseventh SC-FDMA symbols) are calculated by linear interpolationprocessing using channel estimation values calculated based on thereference signals placed in the second and sixth SC-FDMA symbols.

In addition, with the present embodiment, although a case has beenexplained where equalization processing of data received in base stationapparatus 200 is performed in the frequency domain, equalizationprocessing may be performed in the time domain.

Moreover, with the present embodiment, although a SC-FDMA configurationhas been used as an example for explanation, a OFDM (OrthogonalFrequency Division Multiplexing) configuration may be applicable.

Here, with the present embodiment, although one phase table is fixedlyused, the phase table may be changed per cell or may be changed persystem bandwidth.

Here, a case in which the phase table is changed by signaling will beexplained briefly. Reference signals transmitted from the user at highpower is likely to significantly interfere with not only adjacent cyclicshifts but also with cyclic shift positions N cyclic shifts apart.Therefore, the base station detects the presence or absence of users whotransmit broadband SRSs (Sounding Reference Signals) and determinescomplex coefficients for CQI demodulating reference signals inaccordance with cyclic shift positions. That is, the base station andterminals have a plurality of phase table patterns and switch betweenthese tables by signaling.

In a case in which phase tables are changed by signaling, when the usertransmits CQIs and broadband SRSs in the same subframe, the transmissionpower of SC-FDMA symbols for transmitting SRSs (the first SC-FDMA symbolor the seventh SC-FDMA symbol) is greater. Here, if the difference intransmission power between SRSs and CQIs increases, the output of thetransmission amplifier does not stabilize. Therefore, CQI transmissionpower may be increased in order to be adapted to SRS transmission power.

Therefore, the base station determines complex coefficients for CQIdemodulating reference signals in cyclic shift positions in accordancewith the transmission power of users who use resources in the PUCCHfield and designates phase tables used in terminals by signaling.

Embodiment 2

The configuration of terminal apparatus 300 according to embodiment 2 ofthe present invention will be explained with reference to FIG. 12. Here,FIG. 12 differs from FIG. 8 in that radio receiving section 301,demodulating section 302 and decoding section 303 are added, and complexcoefficient multiplying section 113 is changed to complex coefficientmultiplying section 304.

Radio receiving section 301 performs reception processing, includingdown-conversion, A/D conversion and so forth, of signals received viaantenna 120, and outputs the resulting signals to demodulating section302. Demodulating section 302 performs demodulation processing of thereceived signals outputted from radio receiving section 301, and outputsthe received signals to which demodulation processing has been applied,to decoding section 303. Decoding section 303 performs decodingprocessing of the received signal to which demodulating processing hasbeen applied, extracts phase switching signals, and outputs them tocomplex coefficient multiplying section 304.

Complex coefficient multiplying section 304 reads the complexcoefficients corresponding to amounts of cyclic shift (Cyclic shiftindexes) designated by resource allocation information from phase tablestoring section 112. In addition, complex coefficient multiplyingsection 304 switches the read complex coefficients based on phaseswitching signals outputted from decoding section 303.

To be more specific, when the phase switching signal is “0”, complexcoefficients read from the phase table are used. That is, when cyclicshift indexes are even numbers, the phase difference between referencesignals in a slot is zero degrees (complex coefficient {w1, w2}={+1,+1}), and, when cyclic shift indexes are odd numbers, the phasedifference between reference signals in a slot is 180 degrees (complexcoefficient {w1, w2}={+1, −1}).

Meanwhile, when the phase switching signal is “1”, complex coefficients,which have not been read from the phase table, are used. That is, whencyclic shift indexes are even numbers, the phase difference betweenreference signals in a slot is 180 degrees (complex coefficient {w1,w2}={+1, −1}), and, when cyclic shift indexes are odd numbers, the phasedifference between reference signals in a slot is zero degrees (complexcoefficient {w1, w2}={+1, +1}).

For example, the phase switching signal “1” is transmitted to terminalapparatuses using the cyclic shift indexes 0 and 4, and the phaseswitching signal “0” is transmitted to terminal apparatuses using othercyclic shift indexes. This state is shown in FIG. 13.

As described above, complex coefficient multiplying section 304 switchescomplex coefficients in accordance with phase switching signals,multiplies ZAC sequences outputted from ZAC sequence generating section111 by complex coefficients and outputs the results to mapping section114.

Next, the configuration of base station apparatus 400 according toembodiment 2 of the present invention will be explained with referenceto FIG. 14. Here, FIG. 14 differs from FIG. 9 in that CQI transmissionpower detecting section 401, required quality detecting section 402,phase switching signal generating section 403, coding section 404,modulating section 405 and radio transmitting section 406 are added, andcomplex coefficient multiplying section 406 is changed to complexcoefficient multiplying section 407.

CQI transmission power detecting section 401 detects whether or notthere is a user who transmits signals at higher power than other userstransmitting broadband SRSs and CQIs in the same subframe, and, whenthere is the appropriate user, outputs information about the user tophase switching signal generating section 403.

Required quality detecting section 402 detects whether or not there is auser who requires a high quality as compared to other users transmittingCQIs and ACK/NACKs simultaneously, and when there is the appropriateuser, outputs information about the user to phase switching signalgenerating section 403.

Phase switching signal generating section 403 generates phase switchingsignals using user information outputted from CQI transmission powerdetecting section 401, user information outputted from required qualitydetecting section 402, resource allocation information and phase tables.To be more specific, for example, CQI transmission power detectingsection 401 and required quality detecting section 402 report that thetransmission power of the user of CS #2 is high as shown in FIG. 13.Therefore, in order to reduce interference from CS #2, the phaseswitching signal “1” is generated for the users of CS #0 and CS #4,which are cyclic shift indexes two cyclic shifts apart from CS #2, andthe phase switching signal “0” is generated for users of other cyclicshift indexes. The generated phase switching signals are outputted tocoding section 404 and complex coefficient multiplying section 407.

Coding section 404 encodes the phase switching signals outputted fromphase switching signal generating section 403 and outputs the resultingsignals to modulating section 405. Modulating section 405 modulates thephase switching signals outputted from coding section 404 and outputsthe resulting signals to radio transmitting section 406. Radiotransmitting section 406 performs transmission processing, including D/Aconversion, up-conversion, amplification and so forth, of the phaseswitching signals outputted from modulating section 405 and transmitsthe signals to which transmission processing has been applied, fromantenna 201 by radio.

Complex coefficient multiplying section 407 reads the complexcoefficients corresponding to amounts of cyclic shift designated byresource allocation information from phase table storing section 207. Inaddition, complex coefficient multiplying section 407 switches the readcomplex coefficients based on phase switching signals outputted fromphase switching signal generating section 403.

As described above, according to embodiment 2, when there is a user whotransmits broadband SRSs and CQIs in the same subframe, it is possibleto make orthogonal not only reference signals placed in adjacent cyclicshift indexes to each other, but also reference signals placed in cyclicshift indexes one cyclic shift index apart by controlling complexcoefficients read from phase tables, so that it is possible to improvethe capability to receive CQIs and reference signals.

Embodiment 3

Now, the configuration of terminal apparatus 500 according to embodiment3 will be explained with reference to FIG. 15. Here, FIG. 15 differsfrom FIG. 8 in that complex coefficient multiplying section 113 ischanged to complex coefficient multiplying section 501.

Complex coefficient multiplying section 501 determines complexcoefficients in accordance with response signals (ACK/NACKs) of downlinkreceived data. That is, when complex coefficients corresponding tocyclic shift indexes designated by resource allocation information areread from phase table storing section 112, and response signals areNACKs, read values (for example, {w1,w2}={±1, +1}, which make the phasedifference between reference signals in a slot zero degrees when cyclicshift indexes are even numbers) are used as complex coefficients. Inaddition, in a case in which response signals are ACKs, different valuesfrom the read values (for example, {w1,w2}={±1, −1}, which make thephase difference between reference signals in a slot 180 degrees whencyclic shift indexes are even numbers) are used as complex coefficients.FIG. 16 shows an example of allocation of complex coefficient patternswhen CQIs and ACK/NACKs are transmitted simultaneously.

Next, the configuration of base station apparatus 600 according toembodiment 3 of the present invention will be explained with referenceto FIG. 17. Here, FIG. 17 differs from FIG. 9 in that response signaldetecting section 601 is added.

Response signal detecting section 601 measures the power of referencesignals, which are multiplied by complex coefficients assumed asACK/NACK patterns (e.g. {w1, w2}={+1, +1}, {+1, −1}) in multiplyingsection 206 and outputted from mask processing section 214, and detectswhether or not the measured power exceeds a certain threshold. When themeasured power does not exceed the threshold, the step returns tocomplex coefficient multiplying section 206, and coefficient multiplyingsection 206 multiplies reference signals by a different phase patternand response signal detecting section 601 detects whether or not thepower exceeds the threshold. When the measured power exceeds thethreshold, response signal detecting section 601 detects whether signalsare ACKs or NACKs based on the multiplied phase pattern. When the powerdoes not exceed the threshold in all assumed patterns, DTX detectionwill be performed.

As described above, since the base station apparatus cannot clearlyrecognize which pattern is used as ACKs or NACKs in the terminalapparatus, response signal detecting section 601 detects the thresholdof the power of reference signals by which phase patterns aremultiplied, so that it is possible to specify patterns used as ACKs andNACKs in the terminal apparatus.

Here, since CQIs are transmitted only once per several ms, CQIs andACK/NACKs are less likely to be transmitted simultaneously. That is, auser who transmits simultaneously CQIs and ACK/NACKs using given cyclicshifting is highly likely to transmit only CQIs in adjacent cyclic shiftindexes. Therefore, it is possible to improve the capability to receiveNACKs whose required quality is higher than that of ACKs by allocatingcomplex coefficients allowing reduction of interference from adjacentcyclic shift indexes to NACKs and allocating complex coefficients notallowing reduction of interference from adjacent cyclic shift indexes toACKs. Here, 3GPP-LTE has discussed the required quality of an ACK and aNACK. The BLER (Block Error Rates) of an ACK is 10⁻¹ to 10⁻² and that ofa NACK is 10⁻³ to 10⁻⁴.

As described above, according to embodiment 3, it is possible to improvethe capability to receive NACKs whose required quality is higher bymaking the complex coefficient pattern allocated to NACKs transmitted insynchronization with CQIs orthogonal to the complex coefficient patternby which reference signals for transmitting only CQIs are multipliedwhen CQIs and ACK/NACKs are transmitted simultaneously.

Here, with the present embodiment, although a case has been describedwhere feedback is transmitted from response signal detecting section 601in the base station apparatus to complex coefficient multiplying section206 as shown in FIG. 17, this feedback may not be transmitted. In thiscase, response signal detecting section 601 measures power of referencesignals, detects ACKs (NACKs) when the power exceeds the threshold anddetects NACKs (ACKs) when the power does not exceed the threshold.

In addition, with the present embodiment, although a case has beenexplained where response signal detecting section 601 detects powervalues, response signal detecting section 601 may perform quadrantdetection.

Moreover, with the present embodiment, although an example of in-phaseaddition in a base station apparatus has been used, linear interpolationprocessing may be performed as described with embodiment 1.

Here, with each above-described embodiment, CQIs have been used as anexample of information to be transmitted, the present invention is notlimited to this, and data and so forth may be applicable.

Moreover, with each above-described embodiment, although a case has beenexplained where there are two reference signals in one slot, the presentinvention is limited to this, and there may be three or more referencesignals in one slot.

Moreover, with each above-described embodiment, although a unit in whichreference signals used for one channel estimation are placed is referredto as a slot, the unit may be referred to as “frame” and “sub frame”.

Moreover, sequences for reference signals may be quadrature sequencessuch as GCL/ZC sequences, as well as ZAC sequences.

Moreover, although cases have been described with the embodiments abovewhere the present invention is configured by hardware, the presentinvention may be implemented by software.

Each function block employed in the description of the aforementionedembodiments may typically be implemented as an LSI constituted by anintegrated circuit. These may be individual chips or partially ortotally contained on a single chip. “LSI” is adopted here but this mayalso be referred to as “IC,” “system LSI,” “super LSI” or “ultra LSI”depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells within an LSI can be reconfigured is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2008-000197, filed onJan. 4, 2008, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The radio communication terminal apparatus and the radio transmissionmethod according to the present invention allows improvement of thecapability to receive CQIs and reference signals, and is applicable to amobile communication apparatus and so forth.

The invention claimed is:
 1. A communication apparatus comprising: areceiver which, in operation, receives a reference signal, which isgenerated at a terminal apparatus using an index related to a cyclicshift and a pair of coefficients in accordance with a selection signal,wherein the selection signal selects one of a first correspondencerelationship and a second correspondence relationship, each defining arelationship between the index related to a cyclic shift and the pair ofcoefficients, the first correspondence relationship defines a first pairof coefficients corresponding to an even number index related to acyclic shift and a second pair of coefficients corresponding to an oddnumber index related to a cyclic shift and the second correspondencerelationship defines the first pair of coefficients corresponding to theodd number index related to a cyclic shift and the second pair ofcoefficients corresponding to the even number index related to a cyclicshift; and an estimator which, in operation, estimates a channelestimation value using the reference signal.
 2. The communicationapparatus according to claim 1, wherein the first pair of coefficientsis [1 1], and the second pair of coefficients is [1 −1].
 3. Thecommunication apparatus according to claim 1, wherein the referencesignal is generated at the terminal apparatus by determining a pair ofcomplex coefficients according to a table showing a relationship betweenindexes related to the cyclic shift and pairs of coefficients and bymultiplying a signal sequence by the determined pair of complexcoefficients.
 4. A reception method comprising: receiving a referencesignal, which is generated at a terminal apparatus using an indexrelated to a cyclic shift and a pair of coefficients in accordance witha selection signal, wherein the selection signal selects one of a firstcorrespondence relationship and a second correspondence relationship,each defining a relationship between the index related to a cyclic shiftand the pair of coefficients, the first correspondence relationshipdefines a first pair of coefficients corresponding to an even numberindex related to a cyclic shift and a second pair of coefficientscorresponding to an odd number index related to a cyclic shift and thesecond correspondence relationship defines the first pair ofcoefficients corresponding to the odd number index related to a cyclicshift and the second pair of coefficients corresponding to the evennumber index related to a cyclic shift; and estimating a channelestimation value using the reference signal.
 5. The reception methodaccording to claim 4, wherein the first pair of coefficients is [1 1],and the second pair of coefficients is [1 −1].
 6. The reception methodaccording to claim 4, wherein the reference signal is generated at theterminal apparatus by determining a pair of complex coefficientsaccording to a table showing a relationship between indexes related tothe cyclic shift and pairs of coefficients and by multiplying a signalsequence by the determined pair of complex coefficients.